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How to fix a reverse osmosis system leak

We'll locate the leak, replace O-rings or tighten fittings, and tell you when to call a plumber.

How-to · Home plumbing
15–25 min
What you'll need
  • Replacement O-rings (exact match for your RO model)
  • Silicone grease (plumber's grease) (optional)
  • Filter housing wrench (if your model requires one)

At a glance

  • Shut off the water supply and close the tank valve before working on the RO system.
  • Locate the leak—filter housings, membrane housing, fittings, or drain line.
  • Replace worn O-rings with exact matches; hand-tighten housings—do not over-tighten.
  • Tighten loose push-fit or compression fittings; check that tubing is fully inserted.
  • If a housing is cracked or fittings will not seal, replace the part or call a plumber.
Quick triage — pick your path

Get started

Choose the option that matches what you see. You can jump straight to that section.

Steps

Goal: Shut off water, locate the leak, fix O-rings or fittings, and know when to call a plumber.

  • Shut off the cold water supply and close the storage tank valve. Open the RO faucet to relieve pressure.
  • Good: No water flows. Proceed to Locate the leak.
  • Bad: Water still flows—find the correct shutoff valve.

Locate the leak

Goal: Identify where the water is escaping.

  • Dry the filter housings, membrane housing, fittings, and drain line. Turn the water back on briefly and watch where water appears.
  • Good: You see the leak source. Proceed to Replace O-rings or Tighten fittings based on location.
  • Bad: Cannot locate—call a plumber.

Replace O-rings

Goal: Fix leaks at filter or membrane housing seams.

  • Remove the housing cap per your model. Inspect the O-ring for cracks or flat spots. Replace with an exact match, lubricate with silicone grease, and reassemble. Hand-tighten—do not over-tighten. Plastic housings crack easily.
  • Good: No drips at the housing seam. Proceed to Verification.
  • Bad: Housing is cracked—replace the housing or call a plumber.

Tighten fittings

Goal: Stop leaks at push-fit fittings or compression fittings.

  • For push-fit fittings, pull the tubing out, trim a quarter inch off the end, and push back in until it clicks. For compression fittings, check tubing insertion and snug the nut a quarter turn. Check the drain line and saddle valve gasket.
  • Good: No drips at any fitting. Proceed to Verification.
  • Bad: Fittings will not seal—call a plumber.

When to get help

Call a plumber if:

  • A housing is cracked and you cannot get a replacement.
  • Fittings will not seal after tightening.
  • Water is spraying under pressure.

Do not force fittings—you can damage pipes or plastic. For other plumbing fixes, see Fix a water filter that leaks or How to unclog a drain.

Verification

  • No drips at housings, fittings, or drain line when the system runs.
  • The RO faucet produces water at normal flow.
  • The drain line runs without dripping during filter changes or regeneration.

Reviewed by Blackbox Atlas

Frequently asked questions

Why does my RO system leak?
Common causes: worn O-rings in filter or membrane housings, loose push-fit fittings, tubing not fully inserted, or a cracked housing. RO systems have many connections; any one can fail over time.
Can I fix an RO system leak myself?
Yes. Most RO leaks are fixable by replacing O-rings, tightening fittings, or reseating tubing. Shut off the water and tank valve first. If a housing is cracked or you are unsure, call a plumber.
When should I call a plumber for an RO system leak?
Call a plumber if a housing is cracked, fittings will not seal after tightening, or water is spraying under pressure. Do not force fittings—you can damage the plastic components.

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